Merge branch 'branch-1.13.2' into maint
* branch-1.13.2:
docs: '.txi' and '.texinfo' extensions are deprecated
NEWS: document recent documentation improvements
docs: more precise cross reference
docs: 'dist-shar' and 'dist-tarZ' are obsolescent today
docs: improve documentation of 'dist-*' targets slightly
docs: make even clearer 'dist-gzip' is the default.
docs: document 'dist-xz' together with the other 'dist-*' options
docs: 'no-define' option and AM_INIT_AUTOMAKE three-args usage: fixlets
warn: correct broken hyperlink in warning message
Signed-off-by: Stefano Lattarini <stefano.lattarini@gmail.com>